Search results for "Phase"
showing 10 items of 6344 documents
The Role of Elongational Flow in Morphology Modification of Polyethylene/OMMt Nanocomposite System
2011
The formulation of high-performance polymer based nanocomposites depend on many factors, such as polymeric matrix type, nanoparticle type, loading and morphology, affinity between the polymeric matrix and nanoparticles, presence of compatibilizer and processing conditions [1-4]. During the industrial processing the polymer based systems are subjected to two different processing flows, i.e. the shear and elongational flow. The shear flow plays a significant role in polyethylene/OMMt manufacture processing but it is not able to change the system morphology, while, the elongational flow, involved in spinning and film-blowing processing operations, can induce considerably clay morphology variat…
Carbohydrates as Polyfunctional Scaffolds in Combinatorial Synthesis
2006
Carbohydrates are inexpensive, polyfunctional molecules which contain a high density of stereogenic centers. Taking advantage of these particular properties monosaccharides like glucose or mannose have been used for the construction of peptidomimetics which simulate recognition sites of somatostatin or RGD ligands of integrins. Due to their poly functionality, carbohydrates are considered promising scaffolds for combinatorial syntheses either in solution or on solid phase. The application of carbohydrate scaffolds, however, requires sets of orthogonally stable, selectively removable protecting groups, and the challenge in this combinatorial strategy increases with increasing number of hydro…
<title>Optically induced switching of dicyclohexylamino substituted azobenzene derivatives in thin ordered films</title>
2005
During the last years, there has been an increasing interest in the photoinduced switching effects. Among the objects of concern azobenzene derivatives, isomerizing under UV and visible light, occupy a prominent position. To understand the photoresponse of these materials in the condensed phase, their spectroscopic and electrical properties are studied. It is shown that the photoresponse depends on the orientation of the molecules and their packing. A number of novel azobenzene derivatives containing a N,N-dicyclohexyl sulfonamide moiety is synthesized. The derivatives differ in the length of alkyl chains between the azobenzene moiety and SH or COOH groups. The morphology and the photoinduc…
ChemInform Abstract: A Liquid-Liquid Biphasic Homogeneous Organocatalytic Aldol Protocol Based on the Use of a Silica Gel Bound Multilayered Ionic Li…
2012
Key feature of the title protocol is the use of a cis-ion-tagged proline dissolved in a liquid film on a multilayered ionic liquid covalently bound to silica. The resulting catalytically active material is soaked in cyclohexanone and water to form a semi-transparent gel which then reacts with the aldehyde.
Phase selective synthesis of ZnS nanoparticles from structurally new dithiocarbamate precursor
2015
Abstract A phase selective solvothermal synthesis of ZnS (wurzite) nanoparticles with a flower-like morphology using a dithiocarbamate precursor, [Zn(4-dpmpzdtc)2(dpmpz)] (1) (where, dpmpz=(diphenylmethyl)piperazine), is described. The nanoparticles were identified as ZnS (wurzite) with the particle size of about 3 to 10 nm by scanning and transmission electron microscopy as well as powder X-ray diffraction (XRD). In addition, the precursor complex 1 was characterized using single crystal X-ray diffraction.
Separation of aromatic aminophosphonic acid enantiomers by capillary electrophoresis with the application of cyclodextrins
2002
The detailed studies concerning capillary electrophoresis separation of aminophosphonic acid enantiomers with various commercially available cyclodextrins are presented. The obtained results show that the separation of these stereoisomers is dependent on pH of background electrolyte, concentration of cyclodextrin as well as on the type of applied chiral selector. The separation mechanism is based on the co-operative effect of hydrogen bond type interactions enhanced by hydrophobic forces and sterical constrains between aminophosphonate and cyclodextrin. With application of elaborated method, enantiomeric baseline or partial separation of 18 alpha-aminophosphonic acids was achieved. This sep…
Structural Investigation of Water/Lecithin/Cyclohexane Microemulsions by FT-IR Spectroscopy
1995
Abstract FT-IR spectra of water/lecithin/deuterated cyclohexane microemulsions as a function of water/lecithin molar ratio R ( R = [water]/[lecithin]) at various volume fractions ( O ) of the micellar phase have been recorded at 25°C. After elimination of the small spectral contributions due to deuterated cyclohexane and normalization, the shape of the C–H stretching band due to lecithin has been found dependent upon R and O whereas that of the O–H stretching band has been found dependent only upon R . The change in shape of the C–H band was interpreted in terms of a modification of the lecithin alkyl chain packing order. The analysis of the O–H band provides evidence that the hydroxylic gr…
Distribution of volatile organic compounds in Sicilian groundwaters analysed by head space-solid phase micro extraction coupled with gas chromatograp…
2008
This work presents the results of an assessment of the existence and concentration of 13 volatile organic compounds (VOCs) in groundwaters from 14 hydrological basins in Sicily (25,710km (2)). On the basis of hydrological, hydrogeochemical and geological studies, 324 sampling points were selected. All groundwater sampled were collected twice, from October to December 2004 and from February to May 2005, and were analysed to determine the concentration and spatial distribution of the VOCs in the aquifers. The need to analyze a large number of samples in a short space of time so as to obtain quantitative analyses in trace concentration levels spurred us to create a new analytical method, both …
MCM-41 silica monoliths with independent control of meso- and macroporosity
2007
Centimetre sized macroporous silica monoliths consisting of MCM-41 have been prepared by a two-step procedure allowing an independent control of the meso- and macro-porosity. In the first step a monolith with a macroporosity tailored between 2 and 20 μm is prepared under acidic medium by a phase separation, named spinodal decomposition, leading to a bicontinuous structure of a silica/polymer phase and a water phase. The monolith is then reacted in an alkaline solution of cetyltrimethyl ammonium to transform the silica skeleton into MCM-41 under conditions which preserve the original morphology and macroporosity of the material. The combination of spinodal decomposition and pseudomorphic tra…
Transport of amino acids and their phosphonic acid analogues through supported liquid membranes containing macrocyclic carriers. Experimental paramet…
1991
Abstract Amino acid hydrochlorides are well transported through 1-decanol membranes containing Kryptofix 5 or 222 and supported in a porous polyacrylonitrile hollow fiber matrix. Factors which influence the transport of phenylalanine hydrochloride were studied in some detail using this sheet- as well as hollow fibre-supported liquid membranes. These studies show that the choice of the membrane phase, the kind of polymeric support and the mode of membrane preparation are of great importance for the efficiency of the process. The most vital step in the membrane preparation appears to be its activation by soaking in a solution of phenylalanine hydrochloride in a water-ethanol or water-propanol…